package com.school.device.util;

import java.lang.management.ManagementFactory;
import java.net.Inet4Address;
import java.net.InetAddress;
import java.net.NetworkInterface;
import java.util.Enumeration;

import com.mhuang.school.starter.minio.util.ToolUtil;

public class SnowflakeIdeable {
	/**
	 * 时间起始标记点，作为基准，一般取系统的最近时间（一旦确定不能变动）
	 */
	private final long twepoch = 1288834974657L;
	/**
	 * 机器标识位数
	 */
	private final long workerIdBits = 5L;
	/**
	 * 数据中心标识位数
	 */
	private final long datacenterIdBits = 5L;
	/**
	 * 机器ID最大值
	 */
	private final long maxWorkerId = -1L ^ (-1L << workerIdBits);
	/**
	 * 数据中心ID最大值
	 */
	private final long maxDatacenterId = -1L ^ (-1L << datacenterIdBits);
	/**
	 * 毫秒内自增位
	 */
	private final long sequenceBits = 12L;
	/**
	 * 机器ID偏左移12位
	 */
	private final long workerIdShift = sequenceBits;
	/**
	 * 数据中心ID左移17位
	 */
	private final long datacenterIdShift = sequenceBits + workerIdBits;
	/**
	 * 时间毫秒左移22位
	 */
	private final long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;

	private final long sequenceMask = -1L ^ (-1L << sequenceBits);
	/**
	 * 上次生产id时间戳
	 */
	private long lastTimestamp = -1L;
	/**
	 * 0，并发控制
	 */
	private long sequence = 0L;

	/**
	 * 工作id
	 */
	private final long workerId;
	/**
	 * 数据标识id部分
	 */
	private final long datacenterId;

	public SnowflakeIdeable() {
		this.datacenterId = getDatacenterId(maxDatacenterId);
		this.workerId = getMaxWorkerId(datacenterId, maxWorkerId);
	}

	/**
	 * 初始化雪花算法
	 *
	 * @param workerId     工作机器ID
	 * @param datacenterId 序列号
	 */
	public SnowflakeIdeable(long workerId, long datacenterId) {
		if (workerId > maxWorkerId || workerId < 0) {
			throw new IllegalArgumentException(String.format("worker Id can't be greater than %d or less than 0", maxWorkerId));
		}
		if (datacenterId > maxDatacenterId || datacenterId < 0) {
			throw new IllegalArgumentException(String.format("datacenter Id can't be greater than %d or less than 0", maxDatacenterId));
		}
		this.workerId = workerId;
		this.datacenterId = datacenterId;
	}

	/**
	 * 获取下一个ID
	 *
	 * @return 返回下一个ID
	 */
	public synchronized long nextId() {
		long timestamp = timeGen();
		if (timestamp < lastTimestamp) {
			throw new RuntimeException(String.format("Clock moved backwards.  Refusing to generate id for %d milliseconds", lastTimestamp - timestamp));
		}

		if (lastTimestamp == timestamp) {
			// 当前毫秒内，则+1
			sequence = (sequence + 1) & sequenceMask;
			if (sequence == 0) {
				// 当前毫秒内计数满了，则等待下一秒
				timestamp = tilNextMillis(lastTimestamp);
			}
		} else {
			sequence = 0L;
		}
		lastTimestamp = timestamp;
		// ID偏移组合生成最终的ID，并返回ID
		long nextId = ((timestamp - twepoch) << timestampLeftShift) | (datacenterId << datacenterIdShift) | (workerId << workerIdShift) | sequence;

		return nextId;
	}

	private long tilNextMillis(final long lastTimestamp) {
		long timestamp = this.timeGen();
		while (timestamp <= lastTimestamp) {
			timestamp = this.timeGen();
		}
		return timestamp;
	}

	private long timeGen() {
		return SystemClock.now();
	}

	/**
	 * 获取 maxWorkerId
	 *
	 * @param datacenterId 数据中心ID
	 * @param maxWorkerId  最大任务Id
	 * @return 返回16位
	 */
	protected long getMaxWorkerId(long datacenterId, long maxWorkerId) {
		StringBuffer mpid = new StringBuffer();
		mpid.append(datacenterId);
		String name = ManagementFactory.getRuntimeMXBean().getName();
		if (ToolUtil.isNotEmpty(name)) {
			/*
			 * GET jvmPid
			 */
			mpid.append(name.split("@")[0]);
		}
		/*
		 * MAC + PID 的 hashcode 获取16个低位
		 */
		return (mpid.toString().hashCode() & 0xffff) % (maxWorkerId + 1);
	}

	/**
	 * 数据标识id部分
	 *
	 * @param maxDatacenterId 最大的数据中心id
	 * @return 返回随机数
	 */
	protected long getDatacenterId(long maxDatacenterId) {
		long id = 1L;
		byte[] mac = null;
		try {
			Enumeration<NetworkInterface> allNetworkInterfaces = NetworkInterface.getNetworkInterfaces();
			if (null != allNetworkInterfaces) {
				while (allNetworkInterfaces.hasMoreElements() && null == mac) {
					NetworkInterface networkInterface = allNetworkInterfaces.nextElement();
					Enumeration<InetAddress> allInetAddress = networkInterface.getInetAddresses();
					if (null != allInetAddress) {
						while (allInetAddress.hasMoreElements() && null == mac) {
							InetAddress ipAddress = allInetAddress.nextElement();
							if (ipAddress != null && ipAddress instanceof Inet4Address) {
								NetworkInterface network = NetworkInterface.getByInetAddress(ipAddress);
								mac = network.getHardwareAddress();
							}
						}
					}
				}
			}
			if (null != mac) {
				id = ((0x000000FF & (long) mac[mac.length - 1]) | (0x0000FF00 & (((long) mac[mac.length - 2]) << 8))) >> 6;
				id = id % (maxDatacenterId + 1);
			}
		} catch (Exception e) {
			e.getStackTrace();
		}
		return id;
	}

	/**
	 * 生成Id随机数
	 *
	 * @return id随机数
	 */
	public String generateId() {
		return String.valueOf(nextId());
	}
}
